View Full Version : compression

02-27-2007, 05:10 PM
i was wondering what the numbers for compression mean. like if you had 9:1 compression what would that mean?

02-27-2007, 05:15 PM

That's easier than me trying to explain it. :wiggle:

02-27-2007, 05:50 PM
i looked at that for about 20 minutes trying to figure out what that means and still cant figure it out. maybe its better for me not to know

02-27-2007, 06:17 PM
i guess what im trying to ask is what does the 9 mean and what does the 1 mean :wtf:

02-27-2007, 06:40 PM
Let's use easier numbers.

Let's say the engine is a 4.0L 4-cylinder. That's 1 Litre per cylinder. Now, lets say that motor is running a 10:1 compression ratio. That means that when the piston is at the top of the stroke, the remaining space in the cylinder is .1L.

I think that's right.

02-27-2007, 06:46 PM
compression ratio's express how much air/fuel mixture will be compressed during the compression stroke. It's the ratio of the volume in the cylinder above the piston when the piston is at BDC to the volume in the cylinder above the piston when the pistion is at TDC. 9:1 is the total piston displacement + the combustion chamber volume / by the combustion chamber volume.